The concentration of mainstream smoke constituents changes on a puff-by-puff basis starting with the lighting puff and progressing down the rod. It is desirable to selectively reduce certain compounds which occur at significantly higher concentrations in one or two puffs of a cigarette.
Smoke constituent reduction is achieved by resolving from puff-to-puff analysis at which location along a tobacco rod production of a particular smoke constituent is maximized, and locally applying an attenuator at said resolved location to reduce production of the constituent. A remainder of the rod is left untreated so as to minimize impact on taste and burn characteristics of the cigarette.
It is known that taste is dependent on the delivery of total particulate matter (TPM) of cigarette smoke. However, approaches that are applied to the entire cigarette, such as filter ventilation, will reduce smoke components as well as the TPM in the same manner. In this invention, particulate matter from the initial puff can be significantly reduced without significantly effecting the cigarette TPM, thus preserving the taste.
For example, it has been discovered that 40-50% of the formaldehyde found in mainstream tobacco smoke of cigarettes is formed in the first puff. The present invention includes a host of embodiments that address how to adjust a region/zone of the rod corresponding to the first puff such that its contribution of formaldehyde due to pyrolysis/combustion is reduced. It is to be realized that the first puff event is compounded with the act of lighting the cigarette, a process that greatly affects the first puff deliveries of smoke components.
A selective reduction is accomplished by changing the composition of the tobacco filler by only one or two puffs without significantly changing the remaining puffs of the cigarette. In this way, the average delivery level and taste of the cigarette is not changed significantly.
Since 40-50% of the formaldehyde occurs in the lighting or first puff, any one or a combination of cigarette modifications made at the front (lit) end of the tobacco rod will reduce formaldehyde. These modifications include the introduction of an ammonium-source compound, such as ammonium bicarbonate to the tip of the tobacco rod, the addition of alkali metal salts (fire retardants) such as potassium bicarbonate or potassium phosphate, the replacement of a portion of the tobacco blend at the front of the cigarette with a tobacco product having a relatively high level of ammonia, such as Burley, or Bright expanded with ammonia and/or reconstituted tobacco blend (RCB). In addition, yet another approach is to add a reconstituted tobacco blend to the tip in the form of a circular disc attached to the end of the rod. Still another approach is the introduction of ventilation holes or an increase in permeability in the paper outer wrap near the tip to dilute only the lighting puff, and an increase in filler density in the tobacco at the front of the rod.
The amount of formaldehyde formed during a puff is dependent upon the heating rate, the amount of tobacco and char consumed, the temperature of the tobacco prior to the puff, and the amount of condensate on the rod behind the coal. The first puff is distinctly different when considering each of these conditions. The concentration of formaldehyde increases with increasing heating rate. The increase in heating rate of the lighting puff compared to subsequent puffs in which the coal is established results in an increase in concentration. More formaldehyde can be expected to be produced in the first puff because the tobacco is being heated from room temperature whereas in subsequent puffs the tobacco located directly behind the coal is already at elevated temperatures as a result of the static burn. Char that is burnt in these puffs following the lighting puff produces very little formaldehyde compared to tobacco. Because the level of condensate on the cigarette rod in the first puff is significantly less (no accumulation possible from previous puffs) than in subsequent puffs, the effect of rod filtration also is diminished resulting in increased levels of formaldehyde.
In a first embodiment, laser perforations or other forms of perforations are established about the periphery of the free end of the cigarette adjacent the tip. Preferably, the perforations are located sufficient distance to be wholly operative throughout the first puff, but close enough to disappear prior to the second puff. Preferably, the perforations are placed 3 mm to 7 mm from the free end of the cigarette.
If one accepts that approximately 50% of formaldehyde is generated in a particular cigarette during the first puff smoked under FTC conditions, then perforations configured to produce a 50% dilution level (at the tip) may achieve a 25% reduction in the total cigarette delivery of formaldehyde. Too much ventilation at the tip may create difficulties with lighting the cigarette and produce a puff having little or no taste. The pressure drop from the tip of the cigarette to the ventilation holes can be increased by placing a circular piece of RCB rich in ammonium salt or metal foil whose diameter is less than that of the cigarette of the tip.
In another embodiment ammonium salts are utilized in the tobacco rod which release ammonia when heated. The released ammonia reacts with the formaldehydes to remove the latter from mainstream smoke. It is envisioned that the ammonium salts would be added either with or without a solvent, preferably without a solvent. Preferred salts include ammonium bicarbonate, sodium chloride, potassium bicarbonate and potassium phosphate.
With ammonium bicarbonate, one can remove approximately 90% of the 50% first puff contribution of formaldehyde.
Yet another embodiment which utilizes an alkali metal salt (e.g., sodium chloride) to modify the breakdown of cellulose. The cation is believed to be the operative portion of the salt in the chemical events.
In the salt embodiment, such might be mechanically rubbed into free ends of the cigarettes, injected, painted, or applied using a moving orifice device such as described in U.S. Pat. No. 5,997,671 to create striped cigarette paper. The disclosure of U.S. Pat. No. 5,997,671 is incorporated herein by reference. During cigarette making operations, the cigarette rod forming machinery includes registration of the stripes with tobacco rod portions that correspond to the free end portions of the completed cigarettes. Preferably, the stripe is approximately 3 to 7 mm wide or possibly wider.
Another embodiment includes tipping the free end of the cigarette with tobacco having high ammonia, low sugar, such as burley tobacco or some forms of reconstituted tobaccos. Upon lighting a cigarette comprising a plug of Burley tobacco at the tip (or a tip comprising an elevated Burley content), ammonia is released, which reacts with the formaldehyde to alleviate the latter.
Another embodiment includes employment of magnesium ammonium phosphate as filler in paper at the tip or as an addition throughout the tobacco rod or a portion thereof. Copending, commonly assigned, U.S. application Ser. No. 09/399,159, filed Sep. 20, 1999, describes such paper, and text of this application is incorporated herein by reference.
A fundamental aspect of all these embodiments is a process of: resolving at which location along a tobacco rod (corresponding to a one or more of a puff count) where the target (preselected) smoke constituent is maximized; and applying an inhibitor/attenuator of the target smoke constituent at the corresponding rod location. It should be realized that other classes of smoke constituents in either the gas or particulate phases of smoke may maximize at locations other than the free end or tip of the cigarette, and accordingly, the cigarette would be modified at such other locations.
Additionally, it has been discovered that the levels of benzo(a)pyrene (BaP) present in the first puff in mainstream tobacco cigarette smoke approximately equal the sum of the rest of the puffs when using a yellow flame lighting source under laboratory cigarette smoking conditions. Polycyclic aromatic hydrocarbons (PAHs), including BaP, may be reduced in the first or lighting puff by minimizing or eliminating the direct contact of a yellow flame from a match or a gas lighter during lighting. The PAHs produced in the first puff of a cigarette are reduced by lighting with an electric lighter, by modifications made to the cigarette which include attaching a circularly shaped piece of carbon-based and/or metallic material (1 to 2 mm less in diameter than the cigarette) to the center of the tip, replacing the tobacco in the tip with an alternate fuel source that produces no or very low levels of PAHs, placing a catalytic material in the tip to increase the combustion efficiency of the flame, and placing ventilation holes in the paper near the tip as described previously in the discussion on formaldehyde reduction.
The concentration of mainstream smoke constituents changes on a puff-by-puff basis starting with the lighting puff and progressing down the rod. Furthermore, those compounds which occur at significantly higher concentrations in one or two puffs of a cigarette can be reduced selectively by modifying only that portion of the cigarette corresponding to those puff(s). It has been found since then that benzo(a)pyrene, pyrene, phenanthrene, and naphthalene can be at significantly higher levels in the first puff or lighting puff than the other puffs, depending upon the lighting source, the position of the flame to the cigarette tip, and the duration of flame contact during the puff. Lighting a cigarette with a match increases the level of these compounds by a factor of 22, 7, 6 and 4 in the first puff, respectively, compared to an electric lighter. A butane lighter that delivers a yellow flame (indicative of incomplete combustion) increases these compounds in the first puff by a factor of 6, 3, 3, and 3 over an electric lighter. A reference cigarette lit with a yellow flame by a match or with a butane lighter that produces a yellow flame and, which is smoked under FTC conditions, produces an approximately two fold increase in benzo(a)pyrene for the whole cigarette compared to one lit by an electric lighter. It has been discovered that these results with a yellow flame butane lighter are dependent upon position of the cigarette relative to the blue and yellow portions of the flame.
Reduction of the first puff formaldehyde formation is achieved by treating the cigarette tip with salts, using Burley tobacco in the tip, increasing the rod density, ventilation at the tip, and/or thermal treatment of the tip. Reduction of BaP in the first puff of mainstream smoke is achieved by selecting a lighter using a blue flame (not yellow), replacing the tobacco in the tip with an alternate fuel source that produces no or very low levels of PAHs, blocking the end with a thin (xcx9c1 mm) circularly shaped carbon-based disc placed on the tip, placing ventilation holes at the tip, or placing a catalyst in the filler at the tip end. The fact that the first puff is quite different from the rest of the puffs in a cigarette smoking process, in terms of temperature rise, materials consumed, tobacco conditions, and filtration, makes it possible to modify only the portion of cigarette corresponding to the first puff to selectively reduce the compounds that have significantly higher deliveries from the first puff without changing the majority of the cigarette or the smoke chemistry.